Constant tension device for feeding strips such as film



June 27, 1950 I H. N. AIRBANKS 2,513,085

CONSTANT TENS N DEVICE FOR FEEDING STRIPS SUCH AS FILM Filed May 1', 1947 Int P272 01 jsnyflFazrbank-s- MWMM Patented June 27, 1950 CONSTANT TENSION DEVICE FOR FEEDING STRIPS SUCH AS FILM Henry N. Fairbanks, Brighton; N. -Y.. assignor to Mitchell Camera Corporation, Glendale, Calif., a corporation of Delaware Application Mayl 1, 1947, Serial No. 74.5,265'

11 Claims. 1

This. a ppli cationis a continuationinpart of my application Ser. No. 618,161, filed September 24;, 1945,. now abandoned.

The general purpose. and ohjectiveof this .in-v vention is to provide. an automatically acting means whereby uniform tension is .maintained upon a film or the likebya take-up or similar device. Although the inventionis applicable and useful. in any type of mechan ism. where along strip is fed from, or taken up by a winding; reel, the present illustrative and preferred form of the invention has been desi ned particularly usein ki-netograph mechanisms for taking up motion picture film. The inventionwill therefore be de-, scribed primarily as applied to that use, butv with out implying limitation thereto.

Devices have been roposed for the purpose of maintaining uniform take-up tensionon,a,- film, but as far as is known, only one ,previoustype of device hasregulated the tension on the under direct control of the tension itself, all other previous devices depending for actuation and .con-. trol on other factors. such as the weight or size of the instant coil filmon the takeeu-preelr The one previous type which utilizes-the film tension.- for purposes of control, employs an idler roller hanging in a loop. of film between, thetakeeup spool anda positive film feeding roll., The weight of the idler roller, or downwardly exerted spring pressure on it, establishes tension on the in the loop. And movement of theroller withvaria, tions in loop length is then, utilized through ,lever-. age or similar connectionsto control .a frictional clutch through which the takeeup reel or spool is over-driven.

The present invention provides .a much more simple and dependable operating means, controlled directly by the film tensionitself, to main-v tain the tension constant. How thatis done and the nature of the invention itself, willibe best understood from the following detailed .descrip tionof. a present preferred and illustrative, form which is shown in the. accompanying drawings, in which:

Fig. 1 is a diagram showing the general arrangement of a. typical kinetograph mechanism to which the invention is applied;

Fig.2 is an enlarged, section taken as indicated by line 2--2 of Fig. 1, and

Fig. 3. is a section taken asindicatedbyline 33 on Fig.2.

The diagram of Fig. 1 shows. a fil -m movement It! and two film feeding sprockets I l and 12 which are driven by gearing I3, I from driving shaft l 5'. T jke lpspool It is. shown as being driven by a belt I! from the shaft of .taherupssprocket 42,.

while supply spool I8 is shown-as being. freeto rotate as film F ispulled oif'of-it. The-driving; belt ll' for the take-up spool I5, operates ovezza pulley l9 on the shaft of sprocket, l2 andapulley 20, on the shaft of take-up spool I6 The-ratio of that belt drive'is; such-that with; pulley H1 rotating at the full speed of sprocket I-2, .take,-up spool l6-is overdriven. Commonly some-kind-ofi a simple frictional: slip is, providedin that overs drive, but with a slippage; at, any.- given-torque the tension on film F varies inversely with the-di ameter of the. roll' of film on; the take-up spool. In the present invention (as.applied-totake-upsi the ratio. of the take-up drive issuch as1 to, overdrive the spool at alltimes, andat present a belt drive is utilized. The controlled slippage of} a pre-. ferred form-ofthe invention does not, however; utilize slippage in the belt drive itself: Accord ingly the beltdrive may be considered as typical of any suitable driving connectionofthe proper ratio.

, For the purpose of-descriptiorn but: without limitation, it will be assumed that Whenfi is fedforwardly through themechanisml and: ta en upon the take-up spool, the relative'directionsof movement of thevarious. parts are asindicatedr by the several arrows in Fig. 1. Thus it willbe asasumed that the sprocket; [2,.from; which goes directly to. take-up. spool I6, is rotating clocks Wise in Fig.1.

In Fig. 2 shafttll of spool-J2 is shownmounted in a bearing 29- (details explained hereinafter), thatbearing being mounted in a stationarymem: her 28 which may be understood: tohe, a part of the frame ona part of a hired mounting plate in the mechanism- As here shown.- sprocketi I52 is mounted onshaft 30through-:a threaded lens gagement at 3!, so thatthe;sprockeh'exceptfor restraints and; limits which wil-lubei described; is freely rotatable-with referenceto the shaft. Al; the. outer end of shaft 30; a, head 13:2 318 fixed-1y mounted on the shaft to rotate therewith at. all times. A pin or lug.33, fixedly'mountedonv the outer-face of sprocket 12-, projects; into a, circular groove 34 formed in the innerface of head: :3131 This circular groove 3.-lisprovided-zwith apair of stops which are mostconveniently fOIm-Gdfb-N the ends of a semi-circular block 3;5"se.tin groove 34. And a compression spring ;3;6wlies in groove 34 with its opposite ends bearing against. pini:3.3 and one end of block 35.

From a reference to Fig.1. itwil-l .be seen-z'that the take-up tension which. is exerted onnfihrraF by'spool I6 is. a. tension w hichtends toirotate sprocket I2 in the same direction as that in which it is being rotated by the driving mechanism. Take-up spool I6 being frictionally overdriven, the take-up tension on film F tends to pull sprocket I2 ahead. In the particular arrange I ment shown in the drawmgs that direction is j clockwise in Figs. 1 and 3. The tendency to pull the sprocket ahead clockwise moves pin 33 in a y direction to compress spring 36; and spring 36 is chosen of a strength to correspond with the take-up tension desired to be applied to film F.

relative forward rotation of the sprocket, is accommodated by the free loop of film between the movement mechanism I and sprocket I2. As the take-up tension on film F increases sprocket I2 will be rotated further in clockwise direction with reference to shaft 30, compressing spring 35 fur- 1 ther; and as the tension decreases the sprocket will be rotated counter-clockwise Withreference to shaft 30 by spring 36.

Driving gear M for sprocket I2 is here shown as mounted-in its usual position on the other end of shaft 3!? and rigidly afixed thereto, so

I that the gear drives head 32 positively in clockwise direction as viewed in Figs. 1 and 3. Inwardly of driving gear I4 and adjacent its inner face, there is a friction disk 40 which is here shown as carried by a sleeve hub 4i mounted upon another sleeve 42 which in turn is mounted directly on shaft 30. The belt driving pulley I9 isalso here shown as having a sleeve hub it which is mounted on sleeve 42. For the purpose of this invention friction disk 49 and pulley I9 ma be considered as being rotatively fixed to each other. It is only necessary that pulley I9 be driven from friction disk 40 in the direction proper to drive take-up reel I6, which is here assumed to be clockwise as viewed in Figs. 1 and 3. For the purpose of the present invention, friction disk 40 and pulley I9 may be regarded as rotationallysf,

fixed to each other in any manner which provides for the drive of pulley I9 from friction disk 40. Thus, the friction disk and the pulley may be regarded as being both tightly set on sleeve 42 or, equivalently, hubs II and 44 and sleeve 42 may be regarded as integral. And, whatever the arrangement may be to rotatively connect 4| and 44, the friction disk and pulley are freely rotatable with reference to shaft 30 except forthe torque which is applied from the face of gear it through the friction disk. Thus, illustratively sleeve 42 on which both the friction disk and pulley are tightly set, may be regarded as being freely mounted on shaft 30.

Sleeve 42' is preferably shouldered at 45 and bears against an outer end of one of two bearing sleeves 41 which abut each other at their inner ends. These sleeves have flanges 48 at their outer ends which confine the whole shaft mounted mechanism longitudinally with relation to frame plate 28 but which preferably do not frictionally engage the faces of plate 28 or the ends of bearing liner 49. The two bearing sleeves 4'! act as a spacer between the inner face of sprocket I2 and the inner face of the unit which carries friction disk 40.

In the operation of the mechanism, gear I4; shaft 30 and sprocket head 32 are driven at uniform rotational speed in the assumed clockwise direction as viewed in Figs. 1 and 3. For that particular direction of rotation, the screw-threads at 3| are lefthanded, so that an increase in tension on film F which tends to rotate sprocket I2 clockwise in Fig. 1 with relation to shaft 30 will, by the screw-thread action, move sprocket I2 toward the left in Fig. 2 relative to shaft 39, or will allow shaft 30 to move relatively to the right in Fig. 2. Conversely, as the tensionin film F decreases, spring 38 will move sprocket l2 counterclockwise iri Fig. 1 with relation to shaft 30 and will thus draw shaft 30 relatively toward the left in Fig. 2. Friction disk 46 being fixedly spaced from sprocket l2, the forced movement of shaft 30 and gear i i toward the left with relation to the sprocket, when the film tension decreases, causes an increase in the frictional pressure between gear I4 and friction disk 49, to cause an increase in the driving torque applied to belt pulley I9 and therefore to cause'an increase in the tension on the film. And when the sprocket moves relatively counter-clockwise due to decreasing film tension, allowing shaft 30 and gear Is to move relatively to the right in Fig. 2, the frictional pressure, and the tension on film F, are correspondingly relieved. The tension on the film is thus kept substantially uniform.

In normal operation pin 33 floats between such a position as shown in Fig. 3 and a position further around to the right, but without either contacting block 35 or fully compressing spring 36. By proper choice of the pitch of screw 3i a sufficient variation of the frictional torque at the friction faces may be obtained to compensate for the varying diameter of the coil of film on the take-up spool, without pin 33 either abutting the stop block 35 or abutting the effective stop of the fully compressed spring.

The foregoing describes the operation of the constant tension device as applied to a take-up reel or spool. Application to 9, pay-out or supply spool can now be shortly described and easily understood. For this purpose it will be assumed that the system shown in Fig. 1 is operated in the direction opposite to that previously discussed, the film now moving upwardly through movement I0, spool It now being the supply spool, and it and sprocket I2 now rotating counterclockwise. If now spool I6 is retarded in rotation a drag will be exerted on film F to put it in tension corresponding to the amount of retarding drag placed on the spool. That retarding drag can now be obtained, in the mechanism as here shown, by the simple expedient of making the drive (Il, I9, 20) from sprocket shaft 30 to spool I6, of proper ratio to underdrive rather than over-drive the spool. It may be noted that in either case (film being fed either to spool IE, or from that spool) the arrangement tends to rotate spool I6, relative to the rotation of shaft 30 and sprocket [2, in such a direction'as to tend to pull the film from sprocket I2 toward spool It. The force of that tendency, in either case, is the torque transmitted by the friction clutch; an overdriving torque where spool I6 is taking up film, and a dragging torque where the spool is paying out film.

With spool i6 operating to pay out film as described, the mechanism operates to maintain an even tension on the film without any change-other than that stated. Regardless of the now reversed direction of rotation of shaft 30 and sprocket I2, increased tension or pull on the film from spool I6 will rotate sprocket I2 clockwise with relation to shaft 39, and decreased tension will allow spring 36 to rotate the sprocket counterclockwise with relation to the shaft. These relative 2,511 aces rotations are the -sai'ne as before I. described; and; cause thesame controlled adjustmentsixofi torque transmitted by :cl-u'tch plate I 4, to keep the, fi-lm tension-uniformin the same manner.

AI few final observations on the -described; mechanisms will make theirhfunctions.more. clear and-explain thedefinitive expressions-used in, thefollowingclaims n the f rred form of a the. mechanism; as;

here set out, sprocket It i performs:..two distinct; '01" functions; 'a.)J thatofrappl-yi-ng the force of spring l-Z- .tdput. a predetermined ten'sionalpull zonrthe, run of the film betweenl the .sprocket'tand the; spool, in direction tending-to pulluthecfil m. to.-..

ward :the sprocketand; away from the. spool; and -5:

(1).) that of controllably adjusting; the. clutch.

torque byreason. of the .relativev rotationcof; the.

sprocket onits shaft.- v i The first function might berperformedibymeansl known to the .art, leaving;only the;secondtobe;

performed by sprocket l2 For instanceanother. positively. driven filmefeeding sprocket. could be, placed to. the 1eft: of..-sprocl et.-l l;2:.in1Fig.l 1 and .a; dependingloop between the sprocketswould Supm port a. weighted: or. spring loaded roller..: 5.:

With. spring.36.;removed :from. sprocket; It, the loaded loop would then exert. -the predeterminedten'si'onal yieldingpull on the film at nsprocket 1:2,. and thus.exertlacorresponding torque on the.

sprocket, by exerting .thattensional pull on. the; 30.:

film to the left of thesprocket. l.Z-. And-it will be. observedthatin the preferred form of the mechanism, the spring 36 "performs the same functions; it exerts. .y e ina orqpe n t s e and thereby exerts a corresponding yielding ten- -5.

sion on the film at the sprocket Such an arrangement with division of the two functions, although within the broader aspects of the invention, is not preferred. The preferred arrangement with sprocket I2 performingboth functions is much simpler andmuch less liable to disorder and malfunctioning.

The friction clutch represents any suitable form of slippage element capable of transmitting a controllably adjustable torque. Functionally it may be located physically any place in the overdrive or drag which controls the rotation of the spool. Its preferred location however is directly on the shaft of sprocket l2, as that location allows of its control in a very simple manner by the relative rotation of the sprocket on its shaft.

I claim:

1. A constant tension device for mechanisms in which a strip is moved between a roll, which engages the strip non-slippingly, and a spool on which the strip is wound in a spiral coil of varying diameter; said constant tension device comprising a driven roll shaft with relation to which the roll is relatively rotatable, yielding means which exerts on the strip at the roll a predetermined and substantially constant tension and in a direction tending to pull the strip from the spool and tending to rotate the roll relative to its shaft in the corresponding direction, means which tends to cause rotation of the spool relative to rotation of the roll shaft in a direction tending to pull the strip from the roll to the spool and tending to rotate the roll relative to its shaft against said predetermined tension, said means including a slippage unit whose transmitted torque is ad- 7 justable, and means whereby the rotation of the roll relative to its shaft controllably adjusts the torque transmitted by the slippage unit.

2. A constant tension device as defined in claim 1, and in which the yielding means which exerts a from the spools 3; Aconstanttensiondevice; asd'efined in claim 2-, andiin which the/means tending to cause'rotas. tion of the spool. relative. to; rotation, of the-rollsshaft comprises .a. rotary transmission elements freely. mounted on thelroll shaftland connected to: the-spooltorotate it, andafrictional clutch-ante ing between the roll shaft and the transmission, element, one member ofvthe frictional clutch being mounted onthe rolkxshaft; and' in whichcthemeans forcontro1l-ab1y.adjusting thetransmission. torque of a-thefrictional' clutch-comprises a screw. threaded mounting. of the rolli-onits shaftewhere by rel'ativeflrotation of the rolt on its-.shafttcauses relative longitudinal movement-of the shaft-and; thefrictional.clutchmemberl. s

4. A constant tension. device as defi ned-. in.- claim. 1, and in which the means tending to .cause rotationof the: spool relative to rotation. ofuthe roll shaft comprises a. rotary transmission. element. freely. mounted-onthe roll shaft and connectedz'to. thespool to rotateit, and alfrictionahclutcb act i-ng between the. roll, shaft and the. transmission element, one member-of, thefrictional. clutch-ghee, ing mounted zonlthe .rol'L shaft andsintwhich: the; means for controllable adjusting; the transmise sion, torque. of; the, frictionall clutch. comprises.- a screwethreaded mounting ofctherol'l on itsajshafti whereby; relativerotatiort of thelrollzon its shaft: causes relative longitudinal movements of the. shaft andtthe frictional-clutch member,

. ;5.-; 'Azconstant-ltension .devicelfor mechanisms in which. a: strip. is. moi/ed between. a, rel-1,.v engages; the... strip. non-.slippingly, and-. a spoolzonl which the Strip is wound in aspiral; coil; of; vary-e ingsdiameterg; said.- constantutensionidevice;;com-- prisma. roll. driving shaft. on whio'hwtheeroll is, mounted for relative rotation and with means for causing relative longitudinal movement between the roll and shaft by virtue of such relative rotation, a yielding drive transmission element acting between the shaft and the roll, said element yielding to tension exerted on the strip from the spool with resultant rotation and longitudinal movement of the roll relative to the shaft, a transmission between the shaft and the spool tending to cause rotation of the spool relative to rotation of the roll shaft in a direction tending to pull the strip from the roll to the spool, said transmission element including a slippage element of adjustable torque transmission mounted on the shaft, and. means whereby the relative longitudinal movement of the roll on the shaft controllably adjusts the transmission torque of the slippage element.

6. A constant tension take-up device for mechanisms in which a strip is fed forwardly by a constantly driven roll and is taken up from the roll by, and wound in a spiral coil of varying diameter on, a take-up spool; said take-up device comprising, a roll driving shaft on which the feed roll is screw-threadedly mounted, a yielding drive transmission element acting between the driving shaft and the roll, said element yielding to tension exerted on the strip by the take-up spool with resultant rotation and longitudinal translation of the roll relative to the driving shaft, and an overdriving transmission between the driving shaft and the take-up spool including a rotary transmission element freely mounted on the driving shaft, and frictional clutch. means acting be tween the driving shaft and the transmission element and actuated by the relative longitudinal movement of the roll and the shaft.

-7. A take-up device as defined in claim 6,341.1(1; including a roll driving head fixed on an end.

of the shaft and having an innerface opposing an end face of the roll, said head having an'end-i ed annular groove in its said face, and in which the yielding drive transmission element includes a lug projecting from the roll face into the an-, nular groove, and a spring in said groove con 9. A constant tension take-up device for mechanisms in which a strip is fed forwardly by a constantly driven roll and is taken up from the roll by, and wound in a spiral coil of varying diameter on, a take-up spool; said take-up device comprising, a roll driving shaft on one-end of which the feed roll is screw threadedly mounted, a yielding drive transmission, spring acting between the roll and the driving shaft, a bearing in which an intermediate portion of the driving shaft is journalled, a thrust sleeve freely surrounding the shaft and extending through said :bearing and having n end in contact with the inner end of the roll, a driving gear fixedly mounted on the opposite end of the shaft and spaced from the other end of the sleeve, and an overdriving transmission between the driving shaft and the take-up spool including a unit freely mounted on thedriving shaft between the driving gear and the last mentioned end of the sleeve, said unit including a frictiondisk presentinga friction face to the innerface of the driving gear;

and a rotary transmission element which is ro- 3 tatively fixed with reference to the friction disk.

10. A constant tension device for receiving a strip which is fed forward to it from a stripsupply at a positively determinedsupply speed, said device'comprising a, shaft and a roll rotatably mounted with respect to said shaft and adapted to engage the strip non-slippingly, driving means for positively driving said shaft at a speed directly proportional to the strip supply speed and in such direction that when the strip in engagement with the roll is moving forward at the said supply speed the shaft and roll maintain a constant rotational relation, a winding spool adapt,- ed to receive the strip from the roll, yieldingpower transmission means which exerts on the spool a variable torque tending to wind the strip there-j on, transmission control means acting to vary the said torque in accordance with variations in the rotational relation of the'roll and shaft, and yielding means which exerts on the roll a predetermined and substantially constant torque tending to rotate it relative to the shaft in a relatively rearward direction.

11. A constant tension device as defined in claim 10 and in which the said yielding means comprises a yielding force exerting element acting between the roll and the shaft.

HENRY N. FAIRBANKS.

REFERENCES CITED The following references are of record in the file of this patentf UNITED STATES PATENTS Number Name Date Nye Mar. 30, 1937 

